In proscriptive usage, derived adverbs in -ly are often preferred to those which are identical in form to the base adjective (e.g., badly instead of bad), despite the fact that the latter have been in continuous use since the earliest stages of the language and represent the norm in languages closely related to English, such as Dutch and German. This is the cause of hypercorrections such as I feel badly (where feel actually represents a copular verb, which traditionally requires an adjectival complement rather than an adverb).

Various sound changes and spelling changes occur for -ly:

If an adjective ends with the letter y, it changes into i before adding the suffix (e.g. ready, readily).

If an adjective ends with ble, these euphonically blend to bly, due to difficulty of pronouncing *blely. Examples include -ably and -ibly, but also feebly, nimbly, and nobly, among others.